Paribus Co.

Paribus gets you refunds you're owed from stores. When you buy something online and it goes on sale later, stores guarantee to pay you the difference back. Paribus gets you this money back automatically, right from your inbox. Paribus backed by Y Combinator (S15), was acquired by Capital One in 2016, and is already saving money for millions of users. Try it yourself at https://paribus.co